A device for prompting a driver to confirm the driver's attention to driving has been conventionally known. The device detects a decrease in the driver's attention to driving according to driving information such as a vehicle speed, an acceleration, a steering angle or the like, which is detected by sensors. For example, a patent document (JP 2005-104237 A) discloses a drowsy driving prevention device. In the drowsy driving prevention device, an air conditioner blows cold air toward a driver when the device detects a decrease in the driver's attention to driving. Since the driver is exposed to the cold air, an awareness level of the driver increases, and thus, the driver can be prevented from falling into a drowsy driving state.
However, the drowsy driving prevention device in the patent document just provides the cold air when the decrease in the driver's attention is detected. Therefore, the effects for improving the awareness level of the driver may not last a long time. Further, although the drowsy driving prevention device detects the drowsy driving of the driver, the device does not detect an absentminded state in which the driver is not in the drowsy driving state but in a low awareness level state.